Such a scenario occurs frequently: a user A, for example, a smart phone user, needs to contact a user B for a matter, but user A does not have the contact information of user B and is unable to get in touch with user B. As a result, the matter cannot proceed smoothly. From a point of view of user B, he/she may not like to be bothered by any random contact, but would like to receive contacts only for the above-mentioned type of matter. The current technology often cannot meet the needs of both user A and user B.